This type of valve is well known in the prior art. One particularly successful version of the distribution valve is disclosed in U.S. Pat. No. 4,592,379 granted Jun. 3, 1986 to John M. Goettl for "Fluid Distribution Valve". Many of the features disclosed in the Goettl patent are useful in the valve to which this application is directed and, hence, the Goettl disclosure is incorporated herein by reference.
The valve of the '379 patent can be improved upon.